1. Field of the Invention
The present invention is directed to internal combustion engines having tilted cylinders. More particularly, an improved piston oil ring drain arrangement is disclosed.
2. Description of the Related Art
Various conventional internal combustion engines have cylinders tilted at a predetermined angle relative to a vertical axis. In this type of cylinder, lubricating oil may enter the combustion chamber on the piston head side, and remain there when the engine stops. When the engine is started thereafter, the lubricating oil dwelling in the combustion chamber may be flung up in the combustion chamber by a compression ring disposed around the piston body. As a result, the lubricating oil is burned with the fuel, causing white-smoking of the exhaust gas.
A technique to prevent the lubricating oil from entering the combustion chamber is disclosed in, for example, Published Unexamined Japanese Utility Model Application Nos. 53-43107, 53-43108 and 58-146059. In this technique, a baffle or whirl-stop is applied to the piston rings, such as a compression ring and oil ring. Additionally, each ring is secured above the center line of the piston body to thereby inhibit penetration of the lubricating oil.
However, providing the whirl-stop on the piston rings hinders continuous rotation of the piston rings during reciprocation of the piston, thus preventing uniform lubrication between the piston rings and the cylinder. This is because the whirl-stop on the piston rings inhibits their mutual rotation within the ring grooves. Poor lubrication results which prevents the piston rings from moving smootly along the cylinder. In addition, when oil sludge sticks to the piston rings, it can easily cause scuffing between the piston rings and the cylinder, producing a vertical scratch on the cylinder.